The present invention is directed to seamless polymeric belts and to a process for preparing such belts. More specifically, the present invention is directed to seamless belts comprising a laminate of a host polymer and a conducting polymer, and to processes for preparing these belts by the electrochemical deposition of a conducting polymer and the electrophoretic deposition of a host polymer from a a dispersion or emulsion onto an electrode. The present invention is also directed to electrophotographic and ionographic imaging members containing these seamless belts, and to imaging processes employing these members. One advantage of the betls of the present invention is the separation of the electronic conductivity properties and the physical and mechanical properties to the belt as a result of the two different polymers, thereby permitting independent optimization of both characteristics.
Imaging members for electrophotographic imaging systems comprising selenium alloys vacuum deposited on rigid aluminum substrates are known. These imaging members require elaborate, highly sophisticated, and expensive equipment for fabrication. Imaging mumbers have also been prepared by coating rigid substrates with photoconductive particles dispersed in an organic film forming binder. Coating of rigid drum substrates has been effected by various techniques such as spraying, dip coating, vacuum evaporation, and the like. Rigid drum imaging members, however, limit apparatus design flexibility, are less desirable for flash exposure, and are expensive. Flexible organic imaging members are manufactured by coating a web and thereafter shearing the web into segments which are then formed into belts by welding opposite ends of the sheared web. The resulting welded seam on the imaging member, however, disrupts the continuity of the outer surface of the imaging member and must be indexed so that it does not print out during an imaging cycle. Efficient stream feeding of paper and throughput are thus adversely affected because of the necessity to detect a seam within the length of each sheet of paper. The mechanical and optical devices required for indexing add to the complexity and the cost of copiers, duplicators, and printers, and reduce the flexibility of design. Welded belts are also less desirable for electrophotographic imaging systems because the seam forms a weak point in the belt and collects toner and paper debris during cleaning, particularly with wiper blade cleaning devices.
Accordingly, seamless belts suitable as substrates for electrophotographic or ionographic imaging members are particularly desirable. In addition, seamless belts exhibiting conductivity are particularly desirable as substrates for electrophotographic or ionographic imaging members because the conductive portion of the substrate can function as a ground plane in an imaging member. The present invention provides seamless belts exhibiting conductivity on one surface; these belts are suitable substrates for imaging members. In addition, the seamless belts of the present invention are suitable image receptors for ionographic imaging proceses, wherein a latent image is formed on a dielectric image receptor by ion deposition, as described in U.S. Pat. Nos. 4,524,371 and 4,463,363, the disclosures of which are totally incorporated herein by reference.
One layer of the seamless belts of the present invention is prepared by electrochemical deposition of a conducting polymer onto an electrode. An electrochemical polymerization process for polymerization of pyrroles, which are conductive, is disclosed U.S. Pat. No. 4,547,270, the disclosure of which is totally incorporated herein by reference. This reference discloses a process wherein pyrroles or mixtures of pyrroles with comonomers are polymerized electrochemically by anodic oxidation of the monomers in solution or dispersion in an electrolyte solvent, in the presence of a conductive salt, with deposition of the pyrrole polymer at the anode. The anode used consists of an electrically non-conductive sheet-like element which can be impregnated with the electrolyte solution and one or more electrically conducting support and contact strips which connects electrically to a current supply for the anode.
In addition, U.S. Pat. No. 4,680,236 discloses an electrodeless heterogeneous polypyrrole composite which consists of a host polymer and polypyrrole deposited on and within the host polymer. An insulating polymer is at least partially impregnated with sufficient pyrrole monomer to become conductive after the monomer is polymerized. The polymerization is a chemical oxidative polymerization ("dip-polymerization") which, if carried out under anhydrous conditions, transforms the insulating polymer into a semiconductive composite consisting essentially of the host polymer containing a first species of conductive polypyrrole and a Group VIII metal halide counterion. Thereafter, the semiconductive composite containing the counterion is used to electrodeposition it a second species of conductive polypyrrole. The composite with the two species of polypyrrole and anions is used in applications wherein a lightweight organic resistance heating element is desired.
Further, U.S. No. 4,617,228 discloses a process for producing electrically conductive composites. An electrically conductive composite comprising a dielectric porous substance and a pyrrole polymer in the pores of the substance is prepared by treating the porous substance with a liquid pyrrole, and then treating the resulting porous substance with a solution of a strong oxidant in the presence of a non-nucleophilic anion. The pyrrole monomer is oxidized to a pyrrole polymer, which precipitates in the interstices of the porous material. Alternatively, the dielectric porous material can first be treated with a solution of strong oxidant and nonnucleophilic anion followed by treatment with liquid pyrrole, to preciptate an electrcially conductive polypyrrole in the pores of the material. The resulting composite the porous material containing polypyrrole is electrically conductive while the other properties of the porous material are substantially unaffected.
Additionally, U.S. Pat. No. 4,697,000 discloses a process for producing electrically conduvtive polypyrrole powder by treating a liquid pyrrole with a solution of a strong oxidant capable of oxidizing pyrrole to a pyrrole polymer, and oxidizing the pyrrole by the oxidant in the presence of a substantially non-nucleophilic anion and precipitating a conductive polypyrrole powder. The strong oxidant and non-nucleophilic anion can be derived from a single compound. The anion serves as a dopant for the polypyrrole. The reaction can be carried out in aqueous solution or in an organic solvent medium.
The host polymer layer of the belts of the present invention is prepared by electrophoretic deposition of the host polymer onto an electrode. U.S. Pat. No. 4,760,105, the disclosure of which is totally incorporated herein by reference, disclosed an emulsion having a discontinuous phase that consists of a water dispersed or water emulsified epoxy resin in water having at least two epoxide groups, a water soluble salt of an imide compound having at least one carboxyl group, and a crosslinking agent; the discontinuous phase has excess epoxide functionality. The continuous phase is water. A method of forming a coating on a conductive substrate is also disclosed in this patent. The substrate and an electrode are immersed into the emulsion and a direct current is applied between the substrate and the electrode to deposit electrophoretically a coating on the substrate of the epoxy resin, the imide compound, and the crosslinking agent. The substrate is removed from the emulsion and is heated to a temperature sufficient to cure the coating.
In addition, U.S. Pat. No. 4,664,768, the disclosure of which is totally incorporated herein by reference, discloses a method of making a laminate by electrophoretically coating a flat mat made from a material selected from graphite, carbon, and mixtures thereof with an electrophoretable polymer in a non-aqueous system. The polymer is cured and the mat is impregnated with a thermosetable resin. The impregnating resin is B-staged to form a prepreg and several prepregs are stacked and cured under heat and pressure to form the laminate.
Further, U.S. Pat. No. 4,642,170, the disclosure of which is totally incorporated herein by reference, discloses a method of electrophoretically depositing a coating of polysulfones or polyethersulfones on a conductive substrate. An amine-free solution is formed in an organic solvent of the polysulfones or polyethersulfons. Subsequently, an emulsion is formed by combining the solution with an organic non-solvent for the polymer which contains up to about 0.6 parts by weight of an organic nitrogen containing base per parts by weight of the polymer. A direct current is then applied between a conductive substrate and the emulsion, which results in the deposition of the polymer on the substrate.
Additionally, U.S. Pat. No. 4,533,448, the disclosure of which is totally incorporated herein by reference, discloses an electrodepositable emulsion which comprises a soluble un-ionized polymer containing an amic acid or amide linking group, a non-electrolyzable organic solvent for the polymer, and a non-electrolyzable organic non-solvent for the polymer The weight ratio of the solvent to the non-solvent is about 0.1 to about 0.5 and the polymer is about 0.4 to about 5% by weight of the weight of the solvent. No amine or surface active agent is used. A workpiece is coated with the polymer by placing it into the emulsion about one-half to about two inches away from the cathode. Constant dc voltage is applied between the cathode and the workpiece until a coating of a desired thickness has been deposited on the workpiece. The workpiece is then removed, dried, and cured.
Further, U.S. Pat. No. 4,474,658, the disclosure of which is totally incorporated herein by reference, discloses a method of making a non-aqueous emulsion from which a polymer can be electrodeposited. A mixture is prepared of about 50 to about 150 parts by weight of a non-aqueous organic, non-electrolyzable, non-solvent for the polymer with about 0.8 to about 1.2 parts by weight of a nitrogen-containing base which can be a tertiary amine, an imidazole, or mixture of a tertiary amine and an imidazole. To the mixture is added a solution of 1 part by weight of the polymer, which can be a polyamic acid, a polyamide imide, a polyimide, a polyparabanic acid, a polysulfone, or a mixture of these polymers. The polymer is in a non-aqueous, organic, non-electrolyzable aprotic solvent such as N-methyl-2-pyrrolidone.
In addition, U.S. Pat. No. 4,425,467, the diclosure of which is totally incorporated herein by reference, discloses a method of making a non-aqueous emulsion from which a polymer can be electrodeposited. A mixture is prepared of about 50 to about 150 parts by weight of a non-aqueous organic, non-electrolyzable, non-solvent for the polymer with about 0.8 to about 1.2 parts by weight of a nitrogen-containing base which can be a tertiary amine, an imidazole, or mixture of a tertiary amine and an imidazole. To the mixture is added a solution of 1 party by weight of the polymer which can be a polyamic acid, a polyamide imide, a polyimide, a polyparabanic acid, a polysulfone, or a mixture of these polymers. The polymer is in a non-aqueous, organic, non-electrolyzable aprotic solvent such as N-methyl-2-pyrrolidone.
U.S. Pat. No. 4,747,992 discloses a process for forming at least one thin, substantially uniform fluid coating comprising polymeric film forming material on a cylindrical mandrel, solidifying the fluid coating to form a uniform solid coating, and separating the uniform solid coating from the mandrel. The coating thus formed can be used as seamless belt substrates in electrophotographic imaging members.
In addition, "An Electrically Conductive Plastic Composite Derived from Polypyrrole and Poly(vinyl Chloride)", M. De Paoli et al., Journal of Polymer Science, Vol 23, pages 1687 to 1698 (1985), the disclosure of which is totally incorporated herein by reference, discloses a process for obtaining an electrically conductive plastic material by the electrochemical polymerization of pyrrole in a poly(vinyl chloride) matrix to form a composite wherein the polypyrrole is uniformly distributed in the poly(vinyl chloride) matrix. Further, "Conductive Composites from Poly(vinyl chloride) and Polypyrrole", M. De Paoli et al., J. Chem. Soc., Chem. Commun., pages 1015 and 1016 (1984), the disclosure of which is totally incorporated herein by reference, discloses process that entails the electrochemical polymerization of pyrrole on a platinum electrode covered with a film of poly(vinyl chloride) to produce a composite polymer film.
William W. Limburg, Santokh S. Badesha, and John S. Facci in "Seamless Conductive Substrate for Electrophotographic Applications," Xerox Disclosure Journal, Vol. 14, No. 2 (1989), disclose a conductive substrate comprising an interpenetrating polymer network comprising an electronically conductive polypyrrole in a host polymer such as polyvinyl chloride. The interpentrating network can be prepared by depositing the host polymer on a cylindrical metallic electrode by electrostatic powder or solvent spray processes, followed by immersing the host polymer and the conductive mandrel in a bath containing a solution of pyrrole in an electrolyte solution and anodically electropolymerizing the pyrrole to deposit conductive polypyrrole throughout the void areas of the host polymer. Alternatively, the pyrrole swelled host polymer can be contated with diethyl selenite to cause the pyrrole to polymerize oxidatively to polypyrrole on contact. Further, an interpenetrating network of polypyrrole can be created by diffusing separated solutions of diethyl selenite and pyrrole in a swelling solvent into the host polymer from opposite sides of the film so that oxidative chemical polymerization of pyrrole occurs within the host polymer where the separated solutions intersect.
While the above described materials and processes are useful for their intended purposes, there continues to be a need for improved, flexible, free standing conductive polymeric films, and more particularly, for seamless belts for various applications, including substrates for electrostatic and ionographic imaging members. There is also a need for conductive seamless belts wherein the function of conductivity and the function of support, which is derived from polymer properties such as flexibility, tensile strength, and elongation modulus, are separated, thereby allowing for independent optimization of the conductivity and the physical properties of the belt.